Transpositional modulation communications between devices

ABSTRACT

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for determining, by a first device, that a second device is within range for direct communications and that the second device is capable of performing transpositional modulation (TM) communications. Determining to use transpositional modulation to send data to the second device. Sending the data to the second device using a TM signal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/864,331, filed on Jan. 8, 2018, which is acontinuation application of U.S. patent application Ser. No. 15/293,910,filed on Oct. 14, 2016, now U.S. Pat. No. 9,867,086, which is acontinuation application of U.S. patent application Ser. No. 15/139,213,filed on Apr. 26, 2016, now U.S. Pat. No. 9,473,983, which are herebyincorporated by reference in their entirety.

BACKGROUND

Carrier modulation techniques are used to transmit information signalsfrom one location to another. Traditional signal modulation techniquesinclude, for example, amplitude modulation (AM), frequency modulation(FM), and phase modulation (PM). In addition, complex modulationtechniques exist that incorporate aspects of AM, FM, and PM such asquadrature phase shift keying (QPSK), amplitude phase shift keying(APSK) and including quadrature amplitude modulation (QAM).

SUMMARY

This specification relates to methods and systems for performingcommunications between transpositional modulation (TM) capable devices.More specifically, the specification relates to methods and systems forconducting electronic communications using TM signals between TM capabledevices. In addition, the specification relates to methods and systemsfor conducting communications between devices using a combinedtraditional modulation and TM signal on the same carrier signal. Inaddition, the specification describes performing device identificationand/or device discovery using TM signals. Although discussed in thecontext of TM, implementations of the present disclosure also may beapplicable to identifying other aspects or characteristics of variousdevices.

In general, innovative aspects of the subject matter described in thisspecification can be embodied in methods that include the actions ofdetermining, by a first device, that a second device is within range fordirect communications and that the second device is capable ofperforming TM communications. Determining to use transpositionalmodulation to send data to the second device. Sending the data to thesecond device using a TM signal. Other implementations of this aspectinclude corresponding systems, apparatus, and computer programs,configured to perform the actions of the methods, encoded on computerstorage devices.

In another general aspect, innovative aspects of the subject matterdescribed in this specification can be embodied in a communicationdevice that includes one or more processors, a receiver coupled to theone or more processors, a transmitter coupled to the one or moreprocessors, and a data store coupled to the one or more processors. Thedata store includes instructions stored thereon which, when executed bythe one or more processors, causes the one or more processors to performoperations including determining that a second device is within rangefor direct communications and that the second device is capable ofperforming TM communications. Determining to use transpositionalmodulation to send data to the second device. Sending the data to thesecond device using a TM signal.

These and other implementations can each optionally include one or moreof the following features. In some implementations, determining to usetranspositional modulation to send the data to the second deviceincludes determining to use transpositional modulation to send the datato the second device based on an amount of network traffic using non-TMsignals.

In some implementations, determining to use transpositional modulationto send the data to the second device includes determining to usetranspositional modulation to send the data to the second device basedon an amount of the data to be sent.

In some implementations, determining to use transpositional modulationto send the data to the second device includes determining to usetranspositional modulation to send the data to the second device basedon a type of the data.

In some implementations, determining to use transpositional modulationto send the data to the second device comprises determining, based onthe data being a direct current (DC) signal, to use transpositionalmodulation to send the data to the second device.

Some implementations include selectively sending data to the seconddevice using TM signals to manage data flow to within a network.

In some implementations, determining that the second device is withinrange for direct communications includes determining that a quality of asignal received from the second device is above a threshold value fordirect communications.

Some implementations include determining that the second device iscapable of performing TM communications by transmitting a transmissionsignal including a carrier signal modulated with a first TM signal tothe second device. Receiving a response signal from the second device inresponse to the transmission signal. And, determining whether theresponse signal includes a second TM signal.

In some implementations, determining whether the response signalincludes the second TM signal includes mixing the response signal with asecond harmonic of a carrier signal of the response signal to produce amixed signal, and comparing the mixed signal to a third harmonic of thecarrier signal of the response signal.

In some implementations, sending the data to the second device using aTM signal includes receiving a signal including a carrier signalmodulated with a non-TM modulation signal. Detecting a frequency of thecarrier signal by performing a carrier extraction (CAREX) process on thesignal. Adding the TM signal to the carrier signal of the receivedsignal to produce a combined signal. Transmitting the combined signal.

Some implementations include determining to use a non-TM modulation tosend second data to the second device and sending the second data to thesecond device using a non-TM signal.

Particular implementations of the subject matter described in thisspecification can be implemented so as to realize one or more of thefollowing advantages. Implementations may provide an efficient processfor identifying TM capable devices. Implementations may increase thebandwidth of signals transmitted using traditional modulation schemes.Implementations may permit the combination of two differently modulatedsignals on a single carrier frequency. Some implementations may permitextraction of carrier signals from a modulated signal with little or noa priori information about the modulated signal. Some implementationsmay be capable of extracting a carrier from a modulated signal withoutregard to the type of modulation used in the modulated signal. In otherwords, some implementations may able to extract carrier signals whilebeing agnostic to the type modulation of an input signal.

The details of one or more implementations of the subject matterdescribed in this specification are set forth in the accompanyingdrawings and the description below. Other features, aspects, andadvantages of the subject matter will become apparent from thedescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B depict example systems in accordance with implementations ofthe present disclosure.

FIG. 2 depicts a block diagram of an example TM signal transmitter inaccordance with implementations of the present disclosure.

FIG. 3A depicts a block diagram of an example carrier extractor inaccordance with implementations of the present disclosure.

FIG. 3B depicts a block diagram of an example frequency detector inaccordance with implementations of the present disclosure.

FIGS. 4A and 4B depict example control signals generated by a carriersignal extraction device.

FIG. 5 depicts a block diagram of an example TM signal receiver inaccordance with implementations of the present disclosure.

FIG. 6A depicts a block diagram of an example TM signal separation andextraction device in accordance with implementations of the presentdisclosure.

FIG. 6B depicts frequency domain representations of signals at variousstages of the TM signal separation and extraction device shown in FIG.6.

FIGS. 7-11 depict example processes that can be executed in accordancewith implementations of the present disclosure.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Implementations of the present disclosure generally relate to methodsand systems for performing communications between transpositionalmodulation (TM) capable devices.

More specifically, implementations provide methods and systems forconducting electronic communications using TM signals between TM capabledevices. For example, a communication device can identify TM capabledevices that are within range for direct communications. Thecommunication device can determine whether to conduct communicationswith other TM capable devices using TM signals or non-TM signals. Insome examples, a communication device can use TM to balance data usagewithin a communication network. In some examples, a communication devicecan prevent degradation in communication quality within a communicationnetwork by balancing the data usage between TM and non-TM signals.

Some implementations provide methods and systems for performing deviceidentification and/or device discovery using TM signals. For example, TMsignals can be transmitted as a device query signal and devices that areTM capable will be able to respond, while non-TM devices may not be ableto respond at all or may not be able to respond with a corresponding TMsignal. In addition, some implementations establish communicationsbetween devices using a combined traditional modulation and TM signal onthe same carrier signal. For example, supplementary information can becarried in a TM signal combined with a traditional modulation signalthat is routinely used for communications between devices. The TM signalwill not interfere substantially with the traditional modulation signal,thereby, increasing the effective bandwidth of the communicationsbetween devices.

Some implementations of the present disclosure relate to methods andsystems for combining TM signals with traditional modulation (non-TM)signals. For example, implementations provide methods and systems forreceiving an existing non-TM signal and adding a TM signal to thecarrier of the non-TM signal with minimal or no interference to thenon-TM signal. For example, an existing non-TM signal can be received bya TM capable communication device. The communication device can extractthe carrier signal from the non-TM signal, modulate the extractedcarrier with additional data using a TM signal, and combine the TMsignal with the received non-TM signal with minimal or no interferenceto the non-TM signal.

Other implementations of the present disclosure generally extract acarrier signal from an existing modulated signal, modulate the extractedcarrier signal with a TM signal, and combine and retransmit the existingsignal with the TM signal on the same carrier signal. Specifically, theimplementations can extract a carrier frequency from a modulated signalin which the carrier signal has been suppressed (e.g., QPSK, QAM, APSK,BPSK). A CAREX (carrier extraction) circuit determines a frequencydifference between the frequency of the CAREX output signal and aweighted average of the carrier frequency of the input signal. Thecalculated difference value is used to continuously tune a signalgenerator to maintain a minimal difference between the weighted averageof the input carrier frequency and the CAREX output. The third harmonicof the extracted carrier is modulated with a data signal generating a TMmodulated signal. The TM modulated signal is heterodyned back to theextracted carrier frequency and combined with the existing modulatedsignal. The combined signal can then be transmitted. Moreover, the TMmodulated signal in the combined signal does not interfere with theexisting signal because the TM modulation is not recognized bydemodulation systems used to demodulate traditional modulation schemes.Instead, the TM signal appears as a slight increase in noise within theexisting signal.

Other implementations of the present disclosure generally receive acombined traditional modulation and TM signal on the same carrier signalthen separate the TM signal from the combined signal. Specifically, theimplementations can separate the existing signal from a combined signalincluding a traditionally modulated signal (the existing signal) and aTM modulated signal. The existing signal can be demodulated from thecarrier signal. An extracted carrier signal can be re-modulated with thedemodulated existing signal to re-create the existing signal alone,absent the TM modulated signal. The re-modulated existing signal can beremoved from the combined signal leaving only the TM modulated signalwhich can be demodulated using TM demodulation techniques describedherein.

As used herein the terms “Transpositional Modulation,” “TM modulation,”“TM,” and “TM signal” refer to a techniques of adding information to acarrier signal without affecting the amplitude, frequency or phase ofthe carrier signal (or a signal that is modulated according to such atechnique). More specifically, for example, the above terms refer to atype of modulation in which information is conveyed by altering (e.g.,transposing, time shifting) a harmonic of a carrier signal. For example,although the present disclosure is generally directed to producingTranspostional Modulation by altering the third harmonic of a carriersignal, in some implementations Transpostional Modulation can beproduced by altering other harmonics of a carrier signal (e.g., a fourthharmonic, fifth harmonic, sixth harmonic, etc.). Furthermore,Transpositional Modulation and/or TM signals are not detectable bytraditional de-modulators, for example, those used for amplitude,frequency, or phase modulated signals.

As used herein the term “real time” refers to transmitting or processingdata without intentional delay given the processing limitations of thesystem, the time required to accurately measure the data, and the rateof change of the parameter being measured. For example, “real time”communication operations within a communication system should be capableof transmitting, receiving, and processing data without intentionaldelay, and without any user perceptible delays. For example, “real time”communications in a system should be capable of processing a video chatsession between two communication devices with little or no perceptibledelay in audio or video data presented to users of the communicationdevices.

FIG. 1A depicts an example system 100 in accordance with implementationsof the present disclosure. The system 100 is a system of communicationdevices 102. The system 100 may be a radio frequency (RF) communicationsystem, a satellite communication system, a landline communicationsystem (e.g., a telephony or cable network), an optical communicationsystem, a computer network, or any other system of communication devices102. The communication devices 102 include systems for modulating acarrier signal with an information signal using traditional modulationtechniques and transmitting and receiving the modulated signal from onecommunication device 102 to/from another. For example, communicationdevice A may be a cellular base station, and communication devices B, C,and D may be mobile devices (e.g., smartphones). Traditional modulationtechniques include, for example, amplitude modulation (AM), frequencymodulation (FM), and phase modulation (PM) in addition to complexmodulation techniques that incorporate aspects of AM, FM, and PM such asquadrature phase shift keying (QPSK), amplitude phase shift keying(APSK) and including quadrature amplitude modulation (QAM). In addition,communication devices B and C include a TM transmitter 104 and a TMreceiver 106. In some examples, a TM transmitter 104 and/or a TMreceiver 106 can be integrated with traditional transmitters andreceivers. The TM transmitter 104 and/or TM receiver 106 can beimplemented as hardware devices (e.g., integrated circuits, chip-sets,application specific integrated circuits (ASIC) or field programmablelogic arrays (FPGA)) or they can be implemented in software (e.g., as asoftware defined radio (SDR)).

The system 100 can receive a traditionally modulated signal 108 andcombine the traditionally modulated signal 108 with a TM modulatedsignal 110 on the same carrier using a TM transmitter 104, thereby,increasing the overall bandwidth of the combined signal 112. The TMmodulated signal 110 can be separated from the combined signal 112 anddemodulated by a TM receiver 106. Likewise, the traditionally modulatedsignal 108 can be separately demodulated with no interference caused bythe TM modulated signal 110. This is possible because TM modulatedsignals are undecipherable by non-TM receivers, instead appearing as aslight increase of noise in traditionally modulated signals.

For example, communication device A may transmit a QAM signal 108 tocommunication device B. The TM transmitter 104 at communication device Bcan receive the QAM signal 108 and extract the carrier signal from theQAM signal 108. The TM transmitter 104 modulates the extracted carriersignal with a TM signal, combines the TM modulated signal 110 with theQAM signal 108, and retransmits the combined signal 112. In someexamples, as described below, the TM transmitter 104 can extract acarrier signal from a traditionally modulated signal 108 (e.g., the QAMsignal) in which the carrier is suppressed and while having little or noa priori information about the carrier signal (e.g., frequency or phaseinformation).

Communication devices C and D can then receive the combined signal 112.The TM receiver 106 of communication device C separates and extracts theTM modulated signal 110 from the combined signal 112, and thendemodulates the TM modulated signal 110 to obtain the TM modulated datasignal. In some examples, as described below, the TM receiver 106separates the TM modulated signal 110 from the combined signal 112 bydemodulating traditionally modulated signal 108 (e.g., the QAM signal),re-modulating the carrier with only the traditionally modulated signal108, and subtracting the re-modulated carrier signal from the combinedsignal 112 leaving only the TM modulated signal 110. On the other hand,communication device D, which does not have a TM receiver 106, will onlydetect and demodulate the traditionally modulated signal 108; not the TMmodulated signal 110.

In some implementations, the carrier signal can be an intermediatefrequency (IF) carrier signal. That is, the carrier signal is notnecessarily at the same frequency of the carrier upon which the signalis ultimately be transmitted, but may be at an IF used internally withina system (e.g., a satellite communication system) as an intermediatestep in either signal transmission or reception. That is, in the case ofsignal transmission, a system may up-convert a combined signal 112 fromthe IF signal to a transmission carrier frequency prior to transmittingthe combined signal 112. Conversely, in the case of signal reception, asystem may down-convert a modulated signal from the transmission carrierfrequency to an IF frequency before separating the TM modulated signal110 from the combined signal 112. In other implementations, an IFcarrier signal may not be used, and the transmission carrier signal canbe modulated with both a traditionally modulated signal and a TMmodulated signal.

In some implementations, because TM signals are not detectable bytraditional receivers, a TM capable device can identify whether otherdevices have TM reception and transmission capabilities by transmittinga carrier signal modulated with a TM signal to the other devices. Forexample, communication device B can send a query signal 114 thatincludes a carrier signal modulated with a TM signal to one or moreother devices (as indicated by dashed line 115), such as communicationdevice C and communication device D. Communication device C, whichincludes a TM transmitter 104 and a TM receiver 106, will be able todetect the TM modulation within the query signal 114. However,communication device D, which does not include a TM transmitter 104 or aTM receiver 106, will detect only the carrier wave of the query signal.Thus, communication device C will be able to respond to the query signal114, but communication device D will not. Communication device C sends aresponse signal 116 to communication device B (as indicated by dashedline 117) that includes a carrier signal modulated with a TM signal.Communication device B will detect the TM signal included in theresponse signal 116 and, thereby, determine that communication device Cis capable of TM communications.

The query signal 114 can include, for example, only a carrier signalwith TM modulation (e.g., signal 110) or a combined signal 112 includinga carrier modulated with both a traditionally modulated signal 108 and aTM modulated signal 110. In some examples, the query signal 114 caninclude instructions requesting information about the other deviceencoded in either a TM modulated signal 110, a traditionally modulatedsignal 108, or both. However, in some examples, the TM modulated signal110 need not include any specific information or instructions because ifanother device is not capable of receiving TM signals the other devicewould not even detect the TM modulated signal 110 or the encodedinformation. Thus, a TM capable device need only send a response signal116 that includes TM modulation to indicate that the device is capableof receiving TM signals.

In implementations in which the query signal 114 includes both atraditionally modulated signal 108 and a TM modulated signal 110,devices that are not capable of TM communications (e.g., communicationdevice A) may send a response to the non-TM portion of the query signal114. However, a response from a non-TM capable device would only includea traditionally modulated signal and not a TM modulated signal.Therefore, to determine whether a responding device was TM capable, thequerying device (e.g., communication device B) would only need todetermine whether the response included a TM modulated signal 110. Ifnot, the response can be ignored.

In some implementations, the query signal 114 can include informationabout the querying device (e.g., communication device B). For example,the TM modulated portion of the query signal 114 can contain informationincluding, but not limited to, characteristics of the device such asidentifying information, location information for the device, routingtables, identifying information for other TM capable devices incommunication with the responding device, network channelcharacteristics (e.g., noise, bandwidth), handshake data, device paringdata, authentication data (e.g., Out-Of-Band (OOB) authentication data),etc.

In some implementations, the response signal 116 can include informationabout the responding device. For example, the TM modulated portion ofthe response signal 116 from a TM capable device (e.g., communicationdevice C) can include information about the device. The information caninclude, but is not limited to, characteristics of the device such asidentifying information, location information for the device, routingtables, identifying information for other TM capable devices incommunication with the responding device, network channelcharacteristics (e.g., noise, bandwidth), handshake data, device paringdata, authentication data (e.g., OOB authentication data), etc. In someexamples, the query signal 114 can include a request for particularinformation about the responding device. For example, the TM modulatedportion of the query signal 114 from the querying device (e.g.,communication device B) can include a request for information about theresponding device. In such examples, a TM capable responding devicewould be able to detect the information request and provide therequested information in a response signal 116.

Communication device B and C can conduct continued communicationsbetween each other using TM signals. For example, after communicationdevice B and C have identified each other as being capable of conducingelectronic communications using TM signals, the two devices can conductfurther communications using TM modulated signals, traditional (non-TM)modulated signals, or both. In some implementations, once communicationdevices B and C recognize each other as being TM capable, the twodevices can conduct communication using TM signals exclusively, forexample, to free non-TM bandwidth in a communication network for use byother devices that are not TM capable.

In some implementations, the communication devices B and C can conductcommunication using TM signals when predetermined conditions exist, forexample, to make more efficient use of bandwidth in a network ofcommunication devices. For example, such predetermined conditions caninclude, but are not limited to, periods of high network data traffic,transmission of particular types of data, or transmission of data thatexceeds a threshold size (e.g., transfers of large amounts of data). Forexample, a period of high network data traffic can be identified whennetwork traffic using non-TM signals reaches a threshold percentage of achannel's bandwidth. Particular types of data can include, for example,data types that use significant portions of a channel bandwidth such asstreaming data (e.g., streaming video or audio), real time data (e.g.,video chat), analog data, and data indicated as high priority (e.g.,emergency notification data).

FIG. 1B depicts an example environment 130 for employing the techniquesdiscussed above. The example environment is described in the context ofcellular communication network (e.g., a cellular communication fronthaul network). It is appreciated, however, that implementations of thepresent disclosure can be realized in other appropriate environments andcontexts including, but not limited to, for example, computer networks,Internet of Things (IoT) networks, computer peripherals (e.g., plug andplay devices), device pairing, authentication protocols, near-fieldcommunications (NFC), inventory systems, broadcast and/or cablecastsystems, satellite systems, self-driving vehicles, autonomous vehiclecommunications (e.g., unmanned aerial vehicles (UAV)), traffic signalpreemption systems (e.g., used by emergency service vehicles), etc.

The environment 130 includes a base station 132 in communication withseveral mobile devices 134, 136, 138 a-138 n. The base station 132 canbe a radio base station (RBS) for a cellular communication system. Thebase station 132 can include cellular transmitters, receivers, andcomputing equipment for processing cellular communications with themobile devices 134, 136, 138 a-138 n. In addition, the base station 132is capable of conducting electronic communications with TM modulatedsignals. For example, the base station 132 can include TM transmitter(s)and TM receiver(s) such as those described below in reference to FIGS. 2and 5, respectively. It is appreciated, however, that in other contextscommunication devices such as a router, server, wireless access point,etc. could perform the operations similar to those described inreference to the base station 132.

The mobile devices 134, 136, 138 a-138 n are associated with respectiveusers 135, 137, 139 a-139 n. The mobile devices 134, 136, 138 a-138 ncan each include various forms of a processing device including, but notlimited to, a laptop computer, a tablet computer, a wearable computer, ahandheld computer, a personal digital assistant (PDA), a cellulartelephone, a network appliance, a smart phone, an enhanced generalpacket radio service (EGPRS) mobile phone, a mobile hotspot, or anappropriate combination of any two or more of these examplecommunication devices or other communication devices. Furthermore,mobile devices 134 and 136 are capable of conducting electroniccommunications with TM modulated signals. For example, the mobiledevices 134 and 136 can each include a TM transmitter and a TM receiversuch as those described below in reference to FIGS. 2 and 5,respectively.

In operation, the base station 132 communicates with mobile devices 134,136, 138 a-138 n that are located within a network cell 133 served bythe base station 132. When the bandwidth of data communicated betweenthe mobile devices 134, 136, 138 a-138 n and the base station 132 (e.g.,network traffic) approaches the data capacity of a communication channel(e.g., wireless frequency band(s)) for the cell 133 the quality ofcommunications between the mobile devices 134, 136, 138 a-138 n and thebase station 132 tends to degrade. For example, communications can belost between a particular one of the mobile devices 134, 136, 138 a-138n and the base station 132 or data transmission rates experienced by themobile devices 134, 136, 138 a-138 n can degrade.

Implementations of the present disclosure may alleviate suchdegradations in communication quality by using TM signals 142 to conductsome of the communications within the network cell 133. For example,because TM signals 142 and non-TM signal 140 appear transparent to eachother by receivers, the TM and non-TM modulated signals can exist withinthe same communication channel while causing little to no interferencewith each other. Consequently, the base station 132 can conduct some orall of its communication with TM capable mobile devices 134, 136 usingTM signals 142, thereby, freeing non-TM channel bandwidth forcommunications with mobile devices 138 a-138 n that are not TM capable.

For example, a base station 132 can identify TM capable mobile devices134, 136 within communication range of the bases station 132 in the cell133. In some examples, the base station 132 can identify TM capablemobile devices 134, 136 using a process similar to that discussed abovein reference to FIG. 1A. For example, the base station 132 can transmitTM query signals and identify mobile devices 134, 136 that are TMcapable by determining which devices respond to the TM query signals. Insome example, the base station 132 can determine whether a TM capabledevice 134, 136 is within range for communications with the base station132 based on location data from a mobile device, based on the strengthof a signal received from the mobile device, or by using a TM capabledevice identification process similar to that discussed above inreference to FIG. 1A (e.g., based on the response signal strength orlocation data included in the response).

The base station 132 can determine whether to communicate with the TMcapable mobile devices 134, 136 using TM signals 142, non-TM signal 140,or a combination of both. For example, the base station 132 may usenon-TM communication signals as a default communication method withmobile devices 134, 136, 138 a-138 n. The base station 132 canincorporate TM signals 142 for communication with the TM capable mobiledevices 134, 136 when a predetermined criteria is met. For example,various predetermined criteria can be used to determine when toincorporate TM communications so as to make more efficient use ofchannel bandwidth. For example, such predetermined criteria can include,but are not limited to, data traffic within a channel in excess of athreshold value, transmissions of particular types of data, ortransmission of data that exceeds a threshold size (e.g., data files ordata packets that exceed a threshold size). For example, if data trafficusing non-TM signal 140 within the cell 133 meets or exceeds apredetermined threshold value, the base station 132 can begincommunicating with the TM capable devices 134, 136 using TM signals 142exclusively or using a combination of TM and non-TM signals. Shiftingsome of the data traffic within the cell 133 to TM signals 142 canalleviate the data traffic using non-TM signals 140 and may, thereby,prevent or reduce any degradation in the quality of communications withthe cell 133. A predetermined threshold value for data traffic can be,for example, a percentage of channel capacity for communication channelswithin the cell. For example, if data traffic within the cell 133reaches 80% of the channel capacity for the cell 133 using non-TMsignals 140, the base station 132 can begin using TM signals 142 tocommunicate with TM capable devices 134, 136.

As another example, if particular types of data or an amount of datalarger than a predetermined size (“large amounts of data”) are beingtransmitted to or from TM capable devices 134, 136, the base station 132or TM capable device 134, 136 can use TM signals 142 to transmit theparticular type of data or the “large amount of data to, for example,prevent data congestion within the cell 133 using non-TM signals 140.For example, particular types of data that can trigger the use of TMsignals 142 can include, but are not limited to, data types that usesignificant portions of a channel bandwidth such as streaming data(e.g., streaming video or audio), real time data (e.g., video chat),analog data (e.g., analog direct current (DC) or alternating current(AC) signals), and data indicated as high priority (e.g., emergencynotification data). In some examples, low bandwidth data (e.g., SMSmessages, text only e-mail messages, etc.) may be prioritized fortransmission using TM signals 142. For example, at times when bandwidthwithin a cell 133 is in high demand (e.g., during a local emergency or alarge public event), low bandwidth messages may be prioritized fortransmission using TM signals 142, for example, to permit more messagetraffic to be transmitted within the cell 133 during such events.

In some implementations, the base station 132 can communicate with TMcapable mobile devices 134, 138 using TM signals 142 regardless of apredetermined criteria. For example, once the base station 132identifies a mobile device 134, 136 as being TM capable, the basestation 132 can conduct communications with such a mobile device 134,136 using TM signals 142 exclusively or using a combination of TM andnon-TM signal 140. In some examples, the base station 132 can balancethe overall amount of data being communicated between TM signals 142 andnon-TM signals 140 within the cell 133. For example, the base station132 can manage its communications with various mobile devices 134, 136,138 a-138 n within the cell 133 so as to balance the total databandwidth used between TM and non-TM signals. In some examples, the basestation 132 can give priority of bandwidth usage to TM capable mobiledevices 134, 136. For example, the base station 132 can manage the datausage within the cell 133 such that TM capable mobile devices 134, 136are allotted higher data rates using TM signals 142 than non-TM capablemobile devices 138 a-138 n using non-TM signals 140. Such an advantagemay be provided because the TM capable mobile devices 134, 136 withinthe cell 133 permit the base station 132 to more efficiently manage datatraffic within the cellular network. In addition, such an advantage mayincentivize increased adoption of TM capable mobile devices 134, 136.

Although the above implementations have been described in reference tonon-TM signals as being a default communication method between a basestation 132 and mobile devices 134, 136, 138 a-138 n within a cell 133,in some implementations TM signals may be used as a defaultcommunication method. For example, the processed described above may bereversed. That is, TM signals may be used as the default method forcommunicating with mobile devices 134, 136, 138 a-138 n within a cell133 and the base station 132 can use processes similar to thosediscussed above to determine whether to use non-TM signals tocommunicate with particular mobile devices 134, 136, 138 a-138 n. Forexample, a base station 132 can use any or all of the above discussedpredetermined criteria to determine when to incorporate non-TMcommunications.

In some implementations, one TM capable mobile device 134 can conductcommunications with another TM capable mobile device 136 directly (asindicated by dashed line 144). For example, mobile device 134 candetermine that mobile device 136 is a TM capable device and is withinrange for direct communications. If the user 135 of mobile device 134desires to call the user 137 of mobile device 136, mobile device 134 canestablish communications with mobile device 136 using TM signals 142.For example, direct communications between mobile devices 134 and 136may be performed using TM signals 142 within the same communicationchannel as non-TM signal 140 communications between the base station 132and mobile devices 138 a-138 n without interfering with the non-TMsignal 140 communications between the base station 132 and mobiledevices 138 a-138 n. In some examples, the mobile devices 134 and 136can conduct direct communications using TM signals 142 in acommunication channel that is not used by the base station 132 (e.g.,the industrial, scientific and medical (ISM) radio bands). In suchexamples, the TM based communications between mobile devices 134 and 136will not affect non-TM communications between mobile devices usingnon-TM signals within the communication channel. In some examples,direct communications between mobile devices 134, 136 may reduce thedata processing load on the base station 132.

In some implementations, a mobile device can determine whether anothermobile device is within range for direct communications by obtaininglocation data for the second mobile device. For example, mobile device134 can obtain location data for mobile device 136 from the base station132 or through the cellular network (e.g., if mobile device 134 and 136are located in different cells). For example, mobile device 134 mayreceive data related to mobile devices associated with contacts storedin a contact list (e.g., a phonebook) on the mobile device 134, and suchdata can include location data. For example, the mobile device 134 canuse location data of other mobile devices to determine their distancefrom the mobile device 134 and whether such mobile devices are in rangefor direct communications. In some examples, if contact data for user137 is stored in a contact list on mobile device 134, mobile device 134can display an icon next to the user's 137 contact data indicating thatmobile device 136 is within range for direct TM communications. In someexamples, user 135 can initiate direct communications with mobile device136 by selecting the icon.

In some implementations, a mobile device can determine whether anotherTM capable mobile device is within range for direct TM communications byusing a process similar to that discussed above in reference to FIG. 1A.For example, mobile device 134 can transmit a TM query signal toidentify other TM capable mobile devices (e.g., mobile device 136) thatare within range for direct communications. The mobile device 134 canidentify TM capable mobile devices that are within range based on thestrength of a response signal received from other mobile devices, basedon the quality (e.g., signal to noise ratio (SNR), or bit error rate(BER)) of the response signal received, based location data included ina response, or based on a combination of any of the preceding threefactors.

For example, mobile device 134 can determine that mobile device 136 iswithin range for direct communications based on comparing a receivedsignal strength to a threshold signal strength value for directcommunications. If, for example, the received signal strength is greaterthan or equal to the threshold value, mobile device 134 can determinethat mobile device 136 is within range for direct communications. Forexample, mobile device 134 can determine that mobile device 136 iswithin range for direct communications based on comparing a quality(e.g., SNR or BER) of a received to a threshold quality value for directcommunications. If, for example, the quality of the received signal isbetter (e.g., greater than for SNR or less than for BER) than or equalto the threshold value, mobile device 134 can determine that mobiledevice 136 is within range for direct communications.

In some implementations, a mobile device can require confirmation fromanother TM capable mobile device that the other TM capable mobile deviceis within range for direct TM communications before initiating direct TMcommunications with the other device. For example, in somecircumstances, one communication device (e.g., mobile device 134) maydetermine that another communication device (e.g., mobile device 136) iswithin range for direct TM communications based one of the abovediscussed processes (e.g., using location data, signal strength, orsignal quality). However, mobile device 136 may determine that mobiledevice 134 is not within range for direct TM communications. Forexample, mobile device 136 may be located in an environment withsignificant electromagnetic noise. For example, mobile device 134 mayreceive a signal from mobile device 136 with a high SNR and/or low BER,however, a signal received by mobile device 136 from mobile device 134may have a low SNR and/or a high BER. Accordingly, in someimplementations, mobile a communication device, such as mobile device134, can wait to conduct direct TM communications with another mobiledevice, such as mobile device 136, until receiving confirmation that theother mobile device has also determined that the two devices are withinrange for direct communications (e.g., that the received signal strengthor received signal quality of both devices is appropriate for directcommunications).

FIG. 2 depicts a block diagram of an example TM signal transmitter 104in accordance with implementations of the present disclosure. The TMtransmitter 104 includes a carrier extraction portion (CAREX) 206, aharmonic generation portion 202, a TM modulating portion 204, and aheterodyning portion 205. The carrier extraction portion includes thecarrier extractor (CAREX) 206. The harmonic generation portion 202includes a second harmonic generator 208 and a third harmonic generator210. The TM modulating portion 204 includes a signal optimizer 212 and aTM modulator 214. And, the heterodyning portion 205 includes a signalmixer 216, a bandpass filter 218, and a power amplifier 220. Inaddition, the TM transmitter 104 includes a signal coupler 222 and asignal combiner 224.

In operation, the TM transmitter 104 receives an existing modulatedsignal (e.g., traditionally modulated signal 108 of FIG. 1). The signalcoupler 222 samples the existing modulated signal and passes the sampleof the existing modulated signal to the CAREX 206. The CAREX 206extracts a carrier signal (f_(c)) from the existing modulated signal.The CAREX 206 is described in more detail below in reference to FIGS.3A-4B. The output of the CAREX 206 is a pure sinusoidal signal at thefundamental frequency of the carrier from the existing modulated signal.In some examples, the CAREX 206 is agnostic to the type of modulationused in the existing modulated signal. That is, the CAREX 206 canextract the carrier signal from an existing modulated signal regardlessof the type of modulation used in the existing modulated signal. In someexamples, the CAREX 206 can extract carrier signals even when thecarrier is suppressed in the existing modulated signal, and can do sowith little or no a priori information about existing modulated signal'scarrier (e.g., frequency or phase modulation information).

The CAREX 206 passes the extracted carrier signal to a second harmonicsignal generator 208 and a third harmonic signal generator 210, whichgenerate signals at the second and third harmonic frequencies (2 f _(c)and 3 f _(c) respectively) of the fundamental carrier frequency (f_(c)).The second and third harmonic signals (2 f _(c), 3 f _(c)) are used bythe TM modulation portion 204 and the heterodyning portion 205 of the TMtransmitter 104 to generate a TM modulated signal and to heterodyne theTM modulated signal to the fundamental carrier frequency (f_(c)).

The TM modulation portion 204 of the TM transmitter 104 modulates thethird harmonic (3 f _(c)) of the carrier signal (f_(c)) with a datasignal to generate the TM modulated signal. The TM modulated signal isthen heterodyned to the frequency of the carrier signal (f_(c)),combined with the existing modulated signal, and outputted to an antennafor transmission.

In more detail, TM modulation portion 204 receives a data signal fortransmission (e.g., a baseband (BB) data signal). The data signal isoptionally processed for transmission as a TM modulated signal by thesignal optimizer 212. In some examples, the signal optimizer 212produces an optional pattern of inversion and non-inversion of themodulating signal, and filters the modulating signal to ensure that thetotal bandwidth of the data signal is within the channel bandwidth ofthe existing modulated signal. In some examples, the signal optimizer212 can include sample-and-hold circuitry and filters to prepare themodulating signal for transmission as a TM modulated signal. In someexamples, the signal optimizer 212 can be bypassed or turned off and on.

The TM modulator 214 modulates the third harmonic (3 f _(c)) of thecarrier signal (f_(c)) with a data signal to generate the TM modulatedsignal. For example, the TM modulator 214 modulates the third harmonic(3 f _(c)) by introducing a variable time delay based on the datasignal. In other words, the TM modulator 214 can use the data signal asa control signal for introducing an appropriate time delay to thirdharmonic (3 f _(c)). As such, an amount of time delay introduced intothe third harmonic (3 f _(c)) represents discrete bits or symbols of thedata signal. The described time delay modulation technique may beconsidered as time-shift modulation and is performed on the thirdharmonic (3 f _(c)) of the intended carrier frequency (3 f _(c)).

The time-shift modulation of the third harmonic (3 f _(c)) produces asingle set of upper and lower Bessel-like sidebands. The inventor hasconfirmed such results in laboratory simulations with an oscilloscopeand spectrum analyzer. Moreover, the bandwidth of these sidebands can belimited to the bandwidth of an intended communication channel by theoptimizer 212 before TM modulation of the signal, as described above.

In some examples, the time delay may be a phase shift. However, thetime-shift modulation described above is not equivalent phasemodulation. As noted above, the inventor has confirmed in laboratorytests that the time-shift modulation only produces a single pair ofupper and lower Bessel-like sidebands. Phase modulation, however,produces a series upper and lower Bessel-like sidebands.

The heterodyning portion 205 prepares the TM modulation signal do becombined with the existing modulated signal and transmitted by thereceiver. The TM modulated signal is then heterodyned (e.g., frequencyshifted) by mixer 216 down to the fundamental frequency of the carriersignal (f_(c)). The mixer 216 multiplies the TM modulated signal withthe second harmonic of the carrier (2 f _(c)) which shifts the TMmodulated signal to both the fundamental carrier signal frequency(f_(c)) and the fifth harmonic frequency of the carrier. The bandpassfilter 218 removes signal at the fifth harmonic frequency as well as anyadditional signals or noise outside of the bandwidth of the TM modulatedsignal centered at the fundamental carrier signal frequency (f_(c)).

The TM modulated carrier signal is amplified by power amplifier 220 andcombined with the existing modulated signal by the signal combiner 224.It may be necessary, in some examples, to adjust the phase of the TMmodulated carrier signal to match the phase of the carrier in theexisting modulated signal before combining the two signals.

FIG. 3A depicts a block diagram of an example CAREX 206 in accordancewith implementations of the present disclosure. The CAREX 206 can beimplemented as a circuit in a device such as a TM transmitter or TMreceiver, for example. In some implementations, the CAREX 206 can beimplemented as a standalone device for installation into in a largersystem (e.g., an application specific integrated circuit (ASIC) or fieldprogrammable logic array (FPGA)). In some implementations, the CAREX 206can be implemented in software, for example, as a set of instructions ina computing device or a digital signal processor (DSP).

The CAREX 206 operates by determining a center frequency of an inputsignal (e.g., either modulated or unmodulated), comparing the centerfrequency to the frequency of a pure sinusoidal signal produced by asignal generator to create a error signal, and adjusting the frequencyof the signal generator output signal based on a control signalgenerated from the error signal until the error signal is minimized.Furthermore, the CAREX 206 does not require a priori information about acarrier signal to extract the carrier signal and can extract carriersignals when the carrier of the modulated signal is suppressed.

The CAREX 206 includes amplitude limiters 302 a, 302 b, filters 304 a,304 b, frequency detectors 306 a, 306 b, signal generator 308,difference circuit 310, and an amplifier 312. The amplitude limiter 302a and filter 304 a condition input signal before the input signal isanalyzed by the first frequency detector 306 a. The amplitude limiter302 a removes any variations in the amplitude of the input signal. Inother words, the amplitude limiter 302 a stabilizes the amplitude of theinput signal. In some examples, the amplitude limiters 302 a, 302 b canbe an analog comparator or an automatic gain control (AGC) circuit. Thefilters 304 a, 304 b are bandpass filters and removes extraneous signals(e.g., harmonics) and noise outside the channel bandwidth of the inputsignal.

The frequency detectors 306 a and 306 b can be frequency discriminatorsor quadrature detectors. The first frequency detector 306 a detects thecenter frequency of the input signal. As shown in the frequency domainplot 320, an input signal produced by traditional modulation techniquesgenerally has symmetric sidebands 322 located on either side of thecarrier frequency 324. The frequency detector 306 a can determine acenter frequency of an input signal based on, for example, thefrequencies of the outer edges of the sidebands 322. Furthermore, thefrequency detector 306 a can use the sidebands 322 of an input signal todetermine the center frequency even if the carrier signal 324 issuppressed, as illustrated by the dotted line.

The signal generator 308 generates a pure sinusoidal signal (e.g., asingle frequency signal) which is provided to a second frequencydetector 306 b. The signal generator 308 can be, for example, a voltagecontrolled oscillator (VCO) such as, but not limited to, a voltagecontrolled LC (inductor-capacitor) oscillator circuit, a voltagecontrolled crystal oscillator (VCXO), or a temperature-compensated VCXO.The second frequency detector 306 b detects the frequency of the outputsignal from the signal generator 308. In some examples, the outputsignal from the signal generator 308 is provided to an amplitude limiter302 b and filter 304 b before being transmitted to the second frequencydetector 306 b. The amplitude limiter 302 b and filter 304 b stabilizeand filter the amplitude of the signal generator output signal similarto amplitude limiter 302 a and filter 304 a.

The output from each of the first and second frequency detectors 306 a,306 b is provided as inputs to the differencing circuit 310. The outputof both the first and second frequency detectors 306 a, 306 b can be, insome examples, a direct current (DC) voltage signal representing thecenter frequency of the input signal and the frequency of the signalgenerator 308 output signal, respectively. The output of the differencecircuit 310 is a error signal representing the difference in frequencybetween the center frequency of the input signal in the signal generatoroutput signal. The error signal (e.g., a DC voltage) is amplified byamplifier 312 and provided as a control signal to the signal generator308. The amplifier 312 can be, for example, a high gain integratingcircuit that integrates the inputted error signal over time to producethe control signal.

The signal generator 308 adjusts the frequency of its output signalbased on the control signal until the frequency of the signal generator308 output is matched to the center frequency of the input signal. TheDC value of the control signal is used to control the frequency of thesignal generator output, as shown in FIG. 4B and described below. Thesignal generator output is provided as the output of the CAREX 206.Frequency domain plot 330 and time domain plot 334 represent an exampleCAREX 206 output signal. As shown, the output signal of the CAREX 206 isa pure sinusoidal signal having a frequency 332 equivalent to thefundamental carrier frequency of the input signal.

In some implementations, the frequency detectors 306 a and 306 b arematched. In some examples, the matched frequency detectors 306 a and 306b have similar frequency to DC output characteristics over changingmodulated input frequencies. In some examples, the matched frequencydetectors 306 a and 306 b have similar thermal and aging properties. Insome examples, the amplitude limiters 302 a and 302 b, and the filters304 a and 304 b are matched.

In some examples, when the error signal is minimized the signalgenerator output is effectively matched to the center frequency of theinput signal. For example, the error signal can be considered asminimized when its magnitude is zero or substantially close to zero(e.g., when the control signal has a magnitude that is negligible inrelation signal magnitudes measurable or usable by components of theCAREX 206). In some examples, the error signal is considered to beminimized when its magnitude is below a threshold value (e.g., an errortolerance threshold).

In some implementations, the CAREX 206 is adapted to extract carrierfrequencies from single sideband signals. In some examples, the CAREX206 includes a controller that offsets the output signal of the signalgenerator 308 by an appropriate offset frequency. For example, theoutput of the frequency generator 308 can be offset after it is fed backto the second frequency detector 306 b, so as to not adversely affectthe control signal. In some examples, the first frequency detector 306 acan be configured to determine a frequency offset based on the bandwidthof the input signal. In such examples, the first frequency detector 306a can adjust the detected frequency by the frequency offset.

FIG. 3B is a block diagram of an example frequency detector 306 inaccordance with implementations of the present disclosure. The frequencydetector 306 illustrated in FIG. 3B is an example quadrature-baseddetector circuit. The frequency detector 306 includes a phase shiftnetwork 350, a signal mixer 352, and a filter 354. The phase shiftnetwork 350 is a frequency sensitive circuit, such as an all passfilter, for example, that causes a phase shift in an input signal thatcorresponds with the frequency of the input signal. In other words, thephase shift network 350 causes a change in the phase angle of the inputsignal relative to the frequency of the input signal. In some examples,the phase shift network 350 is tuned to produce a nominal phase shift of90 degrees (e.g., quadrature to the input signal) for a nominal designfrequency (e.g., a 70 MHz IF for a communication system).

The signal mixer 352 can be, for example, a signal multiplier. Thesignal mixer 352 receives the input signal and an output signal from thephase shift network 350 as inputs. The filter 354 is a low pass filter.

Plot 360 shows example signals at various points in the frequencydetector 306. The input signal (Signal A) is passed to the phase shiftnetwork 350 and the signal mixer 352. Signal A is shown as a sinusoidfor simplicity, however, Signal A can be a modulated signal. Signal B isthe output of the phase shift network 350 and is phase shifted relativeto the input signal (Signal A). The value of the phase shift correspondsto the frequency of Signal A, and is nominally 90 degrees for a designfrequency. Deviations from the design frequency resulting in a phaseshift of Signal B that deviates from the nominal 90 degrees. The inputsignal (Signal A) is mixed with the output of the phase shift network350 (Signal B) to produce Signal C (e.g., Signal C=Signal A×Signal B).Signal C has a DC offset component corresponding to the phase differencebetween Signals A and B, and by extension, to the frequency of Signal A.The low pass filter 354 then removes the high frequency components ofSignal C leaving only the DC component (Signal D). The deviation ofSignal B's phase shift from the a nominal 90 degrees is exaggerated inplot 360 in order to clearly show the resulting DC output signal (SignalD).

FIG. 4A depicts a plot 400 of an example control signal 402 generated inan example CAREX 206. The plotted control signal 402 is an example ofthe input signal to the signal generator 308 of FIG. 3A. The plottedcontrol signal 452 is broken into several regions (406-410). The regionsillustrate a variations 404 in the control signal 402 as the inputsignal to the CAREX 206 is switched between several different inputsignals, each modulated using a different type of modulation. The inputsignal in region 406 is a QPSK modulated signal. The input signal inregion 408 is a QAM modulated signal. The input signal in region 410 isan unmodulated carrier signal. Each of the input signals in regions406-410 is applied to a 70 MHz carrier. The plot 400 illustrates therobustness of the CAREX 206 and its adaptability to extracting carriersignals from various input signals without regard to the types ofmodulation applied to the carrier signal.

FIG. 4B depicts a plot 450 of another example control signal 452generated in an example CAREX 206. The plotted control signal 452 is anexample of the input signal to the signal generator 308 of FIG. 3A. Theplotted control signal 452 is broken into several regions (456-460). Theregions illustrate transitions 454 of the control signal 452 as theinput signal to the CAREX 206 is switched between several differentinput signals, each having a different carrier frequency. The inputsignal in region 456 is a 67 MHz carrier signal. The input signal inregion 458 is a 73 MHz carrier signal. The input signal in region 460 isa 70 MHz carrier signal. The plot 450 illustrates the robustness of theCAREX 206 and its adaptability to extracting different frequency carriersignals. In some implementations, as shown, the CAREX 206 loop can bedesigned for a specific center frequency (e.g., 70 MHz as shown). Forexample, the design center frequency can be a specific carrier frequencyor IF of a communication system such as a satellite or radio frequency(RF) communication system, for example.

FIG. 5 depicts a block diagram of an example TM signal receiver 106 inaccordance with implementations of the present disclosure. The TMreceiver 106 includes a carrier extraction portion (e.g., CAREX 506), aharmonic generation portion 504, a signal separation and extractionportion (SEPEX) device 512, and a TM demodulator 514. As in the TMtransmitter 104, the harmonic generation portion includes a secondharmonic generator 508 and a third harmonic generator 510. In addition,the TM receiver 106 can include a signal splitter 502 to split acombined input signal (e.g. combined signal 112 of FIG. 1) between theTM receiver 106 and a signal receiver for traditional modulated signals.

In operation, the TM receiver 106 receives a combined input signal andprovides the combined signal to both the CAREX 506 and SEPEX device 512.As described above in reference to the TM receiver 106, the CAREX 506extracts a carrier signal (f_(c)) from the combined signal, and thesecond harmonic generator 508 and third harmonic generator 510,respectively, generate second and third harmonics (2 f _(c) and 3 f_(c)) of the extracted fundamental carrier frequency (f_(c)). Both thecarrier signal (f_(c)) and second harmonic signal (2 f _(c)) areprovided to the SEPEX device 512. The third harmonic signal (3 f _(c))is provided to the TM demodulator 514.

The TM demodulation portion 504 separates and extracts the traditionallymodulated signal from the combined signal to obtain the TM modulatedsignal. The SEPEX device 512 provides the TM modulated signal to the TMdemodulator 514, which, demodulates the TM modulated signal to obtain abaseband data signal. The SEPEX device 512 separates and extracts the TMmodulated signal from the combined signal. In some implementations,before outputting the TM modulated signal, the SEPEX device 512heterodynes (e.g., up-shifts) the TM modulated signal to the thirdharmonic frequency (3 f _(c)) for demodulation. The SEPEX device 512 isdescribed in more detail below in reference to FIG. 6.

The TM demodulator 514 uses the third harmonic signal (3 f _(c))provided by the third harmonic generator 210 as a reference signal forTM demodulation. The TM demodulator 514 demodulates the TM signal bysensing the time shifts between TM modulated carrier signal from theSEPEX device 512 and the third harmonic signal (3 f _(c)). In someexamples, the TM demodulator 514 can be a phase detection circuit. Insome implementations, the TM demodulator 514 detects the time shifts bydetermining a correlation between the TM modulated carrier signal andthe third harmonic signal (3 f _(c)) based on, for example, a product ofthe two signals.

FIG. 6A depicts a block diagram of an example TM signal SEPEX device 512in accordance with implementations of the present disclosure. The SEPEXdevice 512 can be implemented as a circuit in a device such as a TMreceiver, for example. In some implementations, the SEPEX device 512 canbe implemented as a standalone device for installation into in a largersystem (e.g., an application specific integrated circuit (ASIC) or fieldprogrammable logic array (FPGA)). In some implementations, the SEPEXdevice 512 can be implemented in software, for example, as a set ofinstructions in a computing device or a digital signal processor (DSP).

In operation, the SEPEX device 512 demodulates the traditionallymodulated signal from the combined signal. Because the TM modulation isnot detected by traditional signal demodulation, the resulting signaldoes not include the TM signal, but only the demodulated data signalfrom the traditional modulation signal. A “clean” (e.g., un-modulated)carrier is then re-modulated with the previously demodulated data signalfrom the traditional modulation signal. The SEPEX 512 computes thedifference between the combined signal and the re-modulated signal toobtain a TM modulated carrier signal. In other words, the SEPEX device512 removes a traditionally modulated signal from the combined signal bydemodulating the traditionally modulated signal, re-modulating a “clean”(e.g., un-modulated) carrier, and subtracting the re-modulated signalfrom the combined signal, thereby, leaving only the TM modulatedcarrier.

The SEPEX device 512 includes a signal demodulator 602, a signalmodulator 604, low-pass filters 606 a, 606 b, a summing circuit 608, adifference circuit 610, a delay circuit 612, a mixer 614, a bandpassfilter 616, and an amplitude limiter 618. The demodulator 602 is anon-TM signal demodulator, and the modulator 604 is a non-TM signalmodulator. That is, the demodulator 602 and modulator 604 aretraditional modulation type (e.g., AM, FM, PM, QAM, APSK, etc.)demodulator and modulator. The demodulator 602 and modulator 604 aredepicted as a complex (e.g., quadrature and in-phase) demodulator andmodulator, however, in some examples the demodulator 602 and modulator604 can be a simple (e.g., single phase) demodulator and modulator.

The operation the SEPEX device 512 is described below in more detail andwith reference to FIGS. 6A and 6B. FIG. 6B depicts frequency domainrepresentations of signals (A-F) at various stages of the SEPEX device512. The demodulator 602 receives the combined signal (A) (e.g. combinedsignal 112 of FIG. 1) as one input, and the carrier signal (f_(c)) fromthe CAREX 506 as a second input. The combined signal includes both atraditionally modulated signal and a TM modulated signal. As shown bysignal (A) in FIG. 6B, the combined signal includes frequency contentfrom both the TM modulated signal and the traditionally modulated signalcentered about the carrier frequency (f_(c)). The demodulator 602demodulates the traditional modulated signal from the combined signalproducing a baseband data signal. As noted above, because the TMmodulation is not detected by traditional signal demodulation, theresulting baseband data signal does not include a TM signal.

In the case of complex modulation, the demodulator 602 demodulates boththe in-phase and quadrature phase of the combined signal producing anin-phase and a quadrature phase baseband data signal. The low-passfilters 606 a and 606 b remove any extraneous signals or noise from thebaseband data signals, for example, harmonics introduced by thedemodulation process. The resulting baseband data signal, shown bysignal (B), includes only the frequency content from the traditionallymodulated signal centered at zero frequency (baseband). Morespecifically, a TM modulated signal does not exist at baseband, andthus, the TM modulated signal is removed by converting the traditionallymodulated signal to baseband.

The modulator 604 receives the baseband data signals (e.g., in-phase andquadrature phase signals) as a first input, and the carrier signal(f_(c)) from the CAREX 506 as a second input. The modulator 604re-modulates the un-modulated carrier signal (f_(c)) from the CAREX 506with the baseband data signals resulting in re-modulated carriers(re-modulated in-phase and quadrature phase carriers) having only thetraditionally modulated signal. The in-phase and quadrature phasere-modulated carriers are combined by the summing circuit 608 (signal(C)). FIG. 6B signal (C) shows the re-modulated signal again centeredabout the carrier frequency (f_(c)). In some examples, the carriersignal (f_(c)) may be phase shifted or delayed to account for delaysintroduced into the baseband data signals during the demodulation andfiltering process. This is to ensure that the resulting re-modulatedsignal is in phase with the combined signal.

The re-modulated signal is subtracted from the combined signal by thedifference circuit 610 removing the traditionally modulated signal fromthe combined signal. The resulting signal, show by signal (D), includesonly the TM modulated carrier signal (f_(c)). The combined signal isdelayed by the delay circuit 612 to account for delays introduced intothe re-modulated signal by the demodulation and re-modulation process.

The TM modulated signal is heterodyned (e.g., up-shifted) to the thirdharmonic (3 f _(c)) by the mixer 614. The mixer 614 multiplies the TMmodulated signal with the second harmonic (2 f _(c)) of the carrier fromthe second harmonic generator 508 producing signal (E). Heterodyning theTM modulated carrier signal (f_(c)) with the second harmonic (2 f _(c))shifts the TM modulated signal to both the third harmonic (3 f _(c)) andthe negative carrier frequency (−f_(c)) (e.g., a phase inverted versionof the TM modulated signal at the carrier frequency). The bandpassfilter 616 removes the phase inverted TM signal at the carrier frequencyleaving only the TM modulated third harmonic (3 f _(c)) (signal (F)),and the optional amplitude limiter 618 removes any variations in theamplitude of the TM modulated third harmonic signal.

In some examples, the SEPEX device 512 can include multiple differenttypes of demodulators 602 and modulators 604. For example, the SEPEXdevice 512 can include FM, PM, and QAM demodulators 602 and modulators604. In such examples, the SEPEX device 512 can also include a controldevice that detects the type of traditional modulation on input signal,and sends the input signal to the appropriate set of demodulator andmodulator.

Although the SEPEX device 512 is described in the context of separatingand extracting a TM modulated signal from a traditionally modulatedsignal, in some implementations, the SEPEX device 512 can be modified toseparate two traditionally modulated signals such as separatingnon-quadrature modulated signals (e.g., in-phase modulated signal) andquadrature modulated signals. For example, a non-quadrature modulatedsignal could be separated and extracted from a combined I/Q modulatedsignal by modifying the SEPEX device 512 shown in FIG. 6A such that onlythe quadrature modulated signal is demodulated and demodulated bydemodulator 602 and modulator 604.

FIG. 7 depicts an example process 700 for identifying TM capable devicesthat can be executed in accordance with implementations of the presentdisclosure. In some examples, the example process 700 can be provided ascomputer-executable instructions executed using one or more processingdevices (e.g., a digital signal processor) or computing devices. In someexamples, the process 700 may be hardwired electrical circuitry, forexample, as an ASIC or an FPGA device. In some examples, the process 700may be executed by a software defined radio (SDR).

A signal that includes a carrier signal modulated with a transpositionmodulation (TM) signal is transmitted (702). For example, the signal canbe transmitted by an electronic device in a query or discovery requestto determine whether devices within range of the signal have TMcapabilities. In some implementations, the transmitted signal caninclude a non-TM signal on the same carrier signal as the TM signal.

A response to the transmitted signal is received (704). For example, asecond device may receive the transmitted signal and send a responsesignal. If the second device has TM receiving and transmittingcapabilities, the second device can send a response that includes acarrier signal modulated with a TM signal. If the second device does nothave TM receiving and transmitting capabilities, the second device willnot be able to detect the TM portion of the transmitted signal.Consequently, a non-TM capable second device can only respond to anon-TM portion of the transmitted signal.

It is determined whether the response signal includes a TM signal (706).For example, upon receiving the response, the transmitting device cananalyze the response to determine whether it includes a TM signal. Thatis, the transmitting device can analyze the response signal to determineif the carrier includes any TM modulation. If the response includes TMmodulation the transmitting device can determine that the second devicehas TM capabilities. If the response does not include TM modulation, thetransmitting device can determine that the second device does not haveTM capabilities.

In some implementations, the response can include information about thesecond device. For example, the second device can include informationabout the device in a TM portion of a response signal. The informationcan include, but is not limited to, characteristics of the second devicesuch as identifying information, location information for the device,routing tables, identifying information for other TM capable devices incommunication with the second device, network channel characteristics(e.g., noise, bandwidth), etc.

In some implementations, TM modulation can be detected in a signal bymixing a received signal with a second harmonic of the carrier signal.As discussed above in reference to FIGS. 5, 6A, and 6B, mixing thereceived signal with a second harmonic of its carrier signal will shiftsthe received signal to both the third harmonic (3 f _(c)) and thenegative carrier frequency (−f_(c)) (e.g., a phase inverted version ofthe received signal at the carrier frequency) in the frequency domain.This mixed signal can be filtered to remove the phase inverted versionthat is at the carrier frequency. Any TM modulation in the receivedsignal can be detected by comparing the filtered mixed signal to anunmodulated third harmonic of the carrier signal. The TM modulation canbe detected by detecting time shifts in the filtered mixed signalcompared with the unmodulated third harmonic of the carrier. Forexample, if time shifts are not detected, then there is likely no TMmodulation. If time shifts are detected, then the received signalincludes TM modulation and the filtered mixed signal can be sent to a TMdemodulator (e.g., TM demodulator 514 of FIG. 5) to be demodulated. Insome implementations, for example when a signal includes a non-TMsignal, a separation and extraction (SEPEX) process (such as thatdescribed above in reference to FIGS. 6A and 6B and below in referenceto FIG. 10) can be performed on the signal to remove the non-TM signal.

FIG. 8 depicts an example process 800 for providing deviceidentification data that can be executed in accordance withimplementations of the present disclosure. In some examples, the exampleprocess 800 can be provided as computer-executable instructions executedusing one or more processing devices (e.g., a digital signal processor)or computing devices. In some examples, the process 800 may be hardwiredelectrical circuitry, for example, as an ASIC or an FPGA device. In someexamples, the process 800 may be executed by an SDR.

A transmission signal that includes a carrier signal modulated with afirst transposition modulation (TM) signal is received (802). Forexample, the transmission signal can be transmitted by an electronicdevice in a query or discovery request to determine whether a devicethat receives the transmission signal (“receiving device”) has TMcapabilities. In some implementations, the transmitted signal caninclude a non-TM signal on the same carrier signal as the TM signal.

The first TM signal is identified within the transmission signal (804).For example, upon receiving the transmission signal, the receivingdevice can analyze the transmission signal to determine whether itincludes a TM signal. That is, the receiving device can analyze thetransmission signal to determine if the carrier includes any TMmodulation. For example, the receiving device can detect and demodulatea TM signal using the processes described above in reference to FIGS.5-7. In some implementations, for example when a transmission signalincludes a non-TM signal, a separation and extraction (SEPEX) process(such as that described above in reference to FIGS. 6A and 6B and belowin reference to FIG. 10) can be performed on the signal to remove thenon-TM signal.

A response signal that includes information encoded within a second TMsignal is sent (806). For example, if the receiving device is TMcapable, the receiving device can send information back to a device thatsent the transmission signal within the TM signal included in a responseto the transmission signal. The information can include, but is notlimited to, characteristics of the receiving device such as identifyinginformation, location information for the device, routing tables,identifying information for other TM capable devices in communicationwith the receiving device, network channel characteristics (e.g., noise,bandwidth), etc.

FIG. 9 depicts an example process 900 for communications betweentranspositional modulation (TM) capable devices that can be executed inaccordance with implementations of the present disclosure. In someexamples, the example process 900 can be provided as computer-executableinstructions executed using one or more processing devices (e.g., adigital signal processor) or communication devices (e.g., base station132 or mobile devices 134, 136 of FIG. 1B). In some examples, theprocess 900 may be hardwired electrical circuitry, for example, as anASIC or an FPGA device. In some examples, the process 900 may beexecuted by an SDR.

A first device determines that a second device is within range fordirect communications with the first device (902). For example, a firstcommunication device can determine that a second communication device iswithin range for direct wireless communications. For example, a cellularbase station can determine that a mobile device (e.g., smartphone,tablet computer, etc.) is within range for direct communications. Asanother example, one mobile device can determine that another mobiledevice is within range for direct communications. In some examples, thefirst device can determine that the second device is within range fordirect communications based on a received signal strength from thesecond device, a response to a query signal (e.g., a TM query signal),or location data (e.g., GPS data) associated with the second device.

The first device determines whether to use TM to send data to the seconddevice (904). For example, the first device can determine whether thesecond device is capable of performing communications using TM by, forexample, performing a process such as process 700 described above. Thefirst device can, for example, use TM signals to communicate with thesecond device to alleviate network traffic using non-TM signals within acommunication channel used by the first device. In some examples, thefirst device determines to use TM based on one or more criteria. Forexample, the first device can determine to use TM based on one or morecriteria such as an amount of data traffic using non-TM signals, a typeof data to be transmitted, and/or an amount of data to be transmitted.For example, if data traffic is above a threshold value in thecommunication channel used by the first device, the first device cansend the data to the second device using TM. Similarly, for example, thecommunication devices can transmit particular types of data using TMsignals (e.g., real-time data).

The first device sends the data to the second device using a TM signal(906). For example, the first device can perform the following steps910-914, the steps 920-924, or a combination of the two sets of steps tosend the data using a TM signal.

In some implementations, a TM signal can be sent to the second device bymodulating a harmonic of a carrier signal (e.g., a third harmonic) withthe data (910). For example, the harmonic of the carrier signal can bemodulated with data transposing or time shifting the third harmonic torepresent data from the data signal (e.g., data bits or symbols), asdescribed above in reference to FIG. 2. The modulated harmonic isheterodyned to the frequency of the carrier signal. For example, themodulated harmonic of the carrier is shifted (e.g., heterodyned) to thefundamental frequency of the carrier signal (912) to produce the TMsignal. For example, the modulated harmonic can be shifted to thefundamental frequency of the carrier signal by mixing it with anotherappropriate harmonic (e.g., a second harmonic) of the carrier signal.The TM signal is transmitted to the second device (914).

In some implementations, a first signal including a carrier signalmodulated with a non-TM signal is received by the first device (920).For example, the first signal can be an existing signal received from athird communication device such as, for example, a non-TM cellularcommunication signal, a broadcast signal, or a signal in the ISMfrequency band. For example, a broadcast signal can be an AM or FM radiosignal, a broadcast or cable cast televisions signal, a satellitecommunication signal (e.g., a satellite television signal, a GPSsignal). In some examples, the first signal is received by acommunication device that includes both traditional and TM receivers andtransmitters.

A frequency of the carrier signal is detected by performing a carrierextraction process (CAREX) on the first signal (922). For example, aCAREX process such as that described in reference to FIGS. 3A-4B and 10can be performed on the first signal to extract the frequency of thecarrier signal from the first signal.

The TM signal (including the data for the second device) is added to thecarrier signal of the first signal to produce a combined signal (924),and the combined signal is transmitted to the second device. Thecombined signal may be received by various different receivers, but onlyTM capable receivers will be able to detect that the TM signal ispresent in the combined signal.

In some implementations, a TM signal is added to a carrier signal bymodulating a harmonic of a carrier signal (e.g., a third harmonic) withthe data (910). For example, the harmonic of the carrier signal can bemodulated with data by transposing or time shifting the third harmonicto represent data from the data signal (e.g., data bits or symbols), asdescribed above in reference to FIG. 2. The modulated harmonic isheterodyned to the frequency of the carrier signal. For example, themodulated harmonic of the carrier is shifted (e.g., heterodyned) to thefundamental frequency of the carrier signal (912) to produce the TMsignal. For example, the modulated harmonic can be shifted to thefundamental frequency of the carrier signal by mixing it with anotherappropriate harmonic (e.g., a second harmonic) of the carrier signal.The TM signal is transmitted to the second device (914).

In some implementations, the phase of the first signal and the TM signalare synchronized before generating the combined signal. For example, thephase of the TM modulated signal can be synchronized with that of areceived non-TM signal before combining the two signals and transmittingthe combined signal. In some examples, the phase of the carrier of theTM signal can be phase matched with the carrier signal of the non-TMsignal before the two signals are combined.

In some implementations, analog data (e.g., DC signals) can beprioritized for transmission using TM signals. For example, TM signalsmay provide a better response to DC data signals than other non-TMmodulation methods. Specifically, non-TM modulation receivers may relyon consistently shifting values to detect and demodulate signals.However, in some examples, a TM signal can be used to encode a DC signalas a constant shift in a harmonic of a carrier signal that can becontinuously detected by a receiver and interpreted as an appropriate DCvalue.

FIG. 10 depicts an example process 1000 for extracting a carrierfrequency from an input signal that can be executed in accordance withimplementations of the present disclosure. In some examples, the exampleprocess 1000 can be provided as computer-executable instructionsexecuted using one or more processing devices (e.g., a digital signalprocessor) or computing devices. In some examples, the process 1000 maybe hardwired electrical circuitry, for example, as an ASIC or an FPGAdevice. In some examples, the process 1000 may be executed by an SDR.

A center frequency of an input signal is detected (1002). For example,the center frequency can be detected based on frequency side lobes ofthe input signal. In some examples, the input signal can include thecarrier signal modulated with the modulation signal. In some examples,the input signal is a carrier signal modulated with a traditionalmodulation signal and a TM modulation signal. A frequency of a secondsignal is detected (1004). For example, the second signal may be theoutput of a signal generator such as, for example, a VCO or a VCXO. Adifference signal (e.g., control signal) is determined based on thecenter frequency of the input signal and the frequency of the secondsignal (1006). For example, the difference signal represents adifference in frequency between the center frequency of the input signaland the frequency of the second signal. In some examples, differencesignal is a DC voltage signal.

The frequency of the second signal is modified based on the differencesignal to provide the carrier signal of the input signal (1008), and thesecond signal is outputted as the carrier signal from the deviceperforming the process 1000 (1010). For example, a difference signal canbe a control signal for the signal generator and can cause the signalgenerator to adjust the frequency of its output signal. The frequency ofthe second signal modified until it is matched to the center frequencyof the input signal. In some examples, the frequency of the secondsignal is matched to the center frequency of the input signal when thedifference signal reaches a minimum value. In some examples, the minimumvalue may be a threshold value indicating that the difference betweenthe frequency of the second signal in the center frequency of inputsignal is within an allowable tolerance. In some examples, the minimumvalue may be a magnitude of the different signal voltage that is belowthe threshold minimum voltage magnitude.

FIG. 11 depicts an example process 1100 for separating TM signals frominput signals that can be executed in accordance with implementations ofthe present disclosure. In some examples, the example process 1100 canbe provided as computer-executable instructions executed using one ormore processing devices (e.g., a digital signal processor) or computingdevices. In some examples, the process 1100 may be hardwired electricalcircuitry, for example, as an ASIC or an FPGA device. In some examples,the process 1100 may be executed by an SDR.

An input signal including a carrier signal modulated with a firstmodulation signal and a second modulation signal is received (1102). Forexample, the first modulation signal may be a traditional type ofmodulation signal such as, for example, FM, AM, PM, QAM, APSK, etc. Thesecond modulation signal may be a TM modulation signal. The firstmodulation signal is demodulated from the input signal (1104). Forexample, the first modulation signal can be demodulated usingtraditional the modulation techniques. Because traditional demodulationtechniques do not recognize TM modulation, the resulting demodulatedfirst modulation signal will not include the TM modulation signal.

The carrier signal is re-modulated using the demodulated firstmodulation signal to generate a third signal (1106). For example, thethird signal includes an un-modulated carrier signal modulated with thefirst modulation signal. The un-modulated carrier signal has the samefrequency as the carrier of the input signal. The first modulationsignal is removed from the input signal by subtracting the third signalfrom the input signal (1108) to extract the second modulation signal(e.g., the TM modulation signal) from the input signal. In someexamples, the input signal must be delayed an appropriate amount of timeto ensure that it is in phase with the third signal. That is, due to thedemodulation and re-modulation process the third signal may be out ofphase with the original input signal. Thus, before subtracting the thirdsignal from the input signal, the input signal can be delayed anappropriate amount of time. The extracted second modulation signal isprovided to a signal demodulator (1110). For example, an extracted TMmodulated signal can be provided to a TM signal demodulator fordemodulation.

While the present disclosure is generally directed to generatingtranspostional modulated signals and demodulating transpostionalmodulated signals using a third harmonic of a carrier signal, in someimplementations transpostional modulated signals can be generated anddemodulated by using other harmonics of a carrier signal (e.g., a fourthharmonic, fifth harmonic, sixth harmonic, etc.).

Implementations of the subject matter and the operations described inthis specification can be realized in analog or digital electroniccircuitry, or in computer software, firmware, or hardware, including thestructures disclosed in this specification and their structuralequivalents, or in combinations of one or more of them. Implementationsof the subject matter described in this specification can be realizedusing one or more computer programs, i.e., one or more modules ofcomputer program instructions, encoded on computer storage medium forexecution by, or to control the operation of, data processing apparatus.Alternatively or in addition, the program instructions can be encoded onan artificially generated propagated signal, e.g., a machine-generatedelectrical, optical, or electromagnetic signal that is generated toencode information for transmission to suitable receiver apparatus forexecution by a data processing apparatus. A computer storage medium canbe, or be included in, a computer-readable storage device, acomputer-readable storage substrate, a random or serial access memoryarray or device, or a combination of one or more of them. Moreover,while a computer storage medium is not a propagated signal; a computerstorage medium can be a source or destination of computer programinstructions encoded in an artificially generated propagated signal. Thecomputer storage medium can also be, or be included in, one or moreseparate physical components or media (e.g., multiple CDs, disks, orother storage devices).

The operations described in this specification can be implemented asoperations performed by a data processing apparatus on data stored onone or more computer-readable storage devices or received from othersources.

The term “data processing apparatus” encompasses all kinds of apparatus,devices, and machines for processing data, including by way of example aprogrammable processor, a computer, a system on a chip, or multipleones, or combinations, of the foregoing. The apparatus can includespecial purpose logic circuitry, e.g., an FPGA (field programmable gatearray) or an ASIC (application-specific integrated circuit). Theapparatus can also include, in addition to hardware, code that createsan execution environment for the computer program in question, e.g.,code that constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, a cross-platform runtimeenvironment, a virtual machine, or a combination of one or more of them.The apparatus and execution environment can realize various differentcomputing model infrastructures, such as web services, distributedcomputing and grid computing infrastructures.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram can, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub-programs, or portions of code). A computer program can be deployedto be executed on one computer or on multiple computers that are locatedat one site or distributed across multiple sites and interconnected by acommunication network.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform actions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. Elements of a computer can include aprocessor for performing actions in accordance with instructions and oneor more memory devices for storing instructions and data. Moreover, acomputer can be embedded in another device, e.g., a mobile telephone, apersonal digital assistant (PDA), a mobile audio or video player, a gameconsole, a Global Positioning System (GPS) receiver, or a portablestorage device (e.g., a universal serial bus (USB) flash drive), to namejust a few. Devices suitable for storing computer program instructionsand data include all forms of non-volatile memory, media and memorydevices, including by way of example semiconductor memory devices, e.g.,EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internalhard disks or removable disks; magneto-optical disks; and CD-ROM andDVD-ROM disks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyimplementation of the present disclosure or of what can be claimed, butrather as descriptions of features specific to example implementations.Certain features that are described in this specification in the contextof separate implementations can also be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation can also be implemented inmultiple implementations separately or in any suitable sub-combination.Moreover, although features can be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination can be directed to asub-combination or variation of a sub-combination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingcan be advantageous. Moreover, the separation of various systemcomponents in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

Thus, particular implementations of the subject matter have beendescribed. Other implementations are within the scope of the followingclaims. In some cases, the actions recited in the claims can beperformed in a different order and still achieve desirable results. Inaddition, the processes depicted in the accompanying figures do notnecessarily require the particular order shown, or sequential order, toachieve desirable results. In certain implementations, multitasking andparallel processing can be advantageous.

What is claimed is:
 1. A method for communications betweentranspositional modulation (TM) capable devices, the method comprising:determining, by a first device, that a second device is within range fordirect communications and that the second device is capable ofperforming TM communications; determining, by the first device, to usetranspositional modulation to send data to the second device; andsending the data to the second device using a TM signal.